In accordance with a rapid spread of information related apparatuses and communication apparatuses such as a personal computer, a video camera and a portable telephone in recent years, the development of a battery to be utilized as a power source thereof has been emphasized. The development of a high-output and high-capacity battery for an electric automobile or a hybrid automobile has been advanced also in the automobile industry. A lithium battery is of interest from the viewpoint of a high energy density compared to other kinds of batteries.
A liquid electrolyte including a flammable organic solvent is used for a conventional commercial lithium battery, so that the installation of a safety device for restraining temperature rise during a short circuit and the structure for preventing the short circuit are necessary therefor. In contrast, a solid state battery such that the liquid electrolyte is replaced with a solid electrolyte layer to provide an all solidify the battery is conceived to simplify the safety device and improve production cost and productivity where the flammable organic solvent is not used in the battery.
In all solid batteries, solid electrode materials (such as active materials, solid electrolytes, and conductive materials) are formed with electrode bodies, so that it is important the materials are adhered to each other in the constitution. For example, Patent Literature 1 discloses a production of a composite active material in which a sulfide solid electrolyte material is mixed with an oxide active material coated with an oxide solid electrolyte layer while applying energy to plastically deform the sulfide solid electrolyte material, so as to form a sulfide solid electrolyte layer on the oxide active material. An object of Patent Literature 1 is to reduce the reaction resistance in batteries. Patent Literature 2 discloses mixing a sulfide solid electrolyte material with an oxide active material coated with an oxide solid electrolyte layer for 10 minutes while adjusting the temperature to 100° C. or less and applying energy to plastically deform the sulfide solid electrolyte material, so as to bring the BET specific surface area of a composite active material to be less than 2.82 m2/g. Patent Literature 3 discloses a technique of forming a coating layer including a sulfide solid electrolyte material in the surface of an active material by conducting a rotation and revolution mixing treatment with respect to a raw material composition including an active material and a sulfide solid electrolyte material. An object of Patent Literature 3 is to form the coating layer while restraining the damage to the active material surface.